How does a sponge filter work?

A sponge filter, at the simplest, is a vertical pipe with holes drilled into it, covered by a sponge, and vertically anchored to the aquarium floor. Inside the pipe, an airstone with airline tubing is attached, with the airstone positioned at the bottom of the pipe.

As air bubbles go up from the airstone, a vacuum is formed. This vacuum will make water go through the sponge and come out with the air bubbles.

As water passes through the sponge, larger particles will be left behind in the sponge’s material, and bacteria inside the sponge will clean up some of the chemical and biological waste. As the water comes out at the top, it should be clean.

It is much easier for you to watch how a DYI sponge filter is made and how it works instead of having me explain it with words, so here are some video tutorials that should help you out:

Making Your Own Sponge Filter

Tutorial 1

In this video, Joey Mullen talks about how sponge filters, while not being the best filter you can get, are easy to make, simple to use and quick to install when you are setting up tanks for quarantine or breeding.

Even better, these filters also work well with battery-powered air pumps, in case of power outages. All of the materials needed will only cost you around $4 to $5.

• Cut hole through sponge; you can use a hot knife, or just a normal knife. Make sure the pipe is a snug fit through the hole.
• Wash ceramic tile, then use the silicone glue/sealant and attach cap to it; leave it alone for 24 hours to make sure the sealant is dry.
• Mark off where sponge will cover the pipe, and drill multiple holes in the area that the sponge will cover (see video for specifics).
• Drill hole on top of 90-degree elbow. This is where the airline tubing will pass through to the internal pipe area.
• Once you pass the tubing through the 90-degree elbow attachment, attach air stone to tubing, and extend tubing until air stone can be put at the “bottom” of the pipe – the end where the pipe will be attached to the end plate. Plug in the elbow attachment to tope of the PVC pipe.
• Insert pipe system into the sponge, and attach the end plate to the pipe. You can also attach another PVC tube to the elbow, so that the bubbles and filtered water will come out farther from the sponge filter.
• You can make the pipe longer, to accommodate more sponges, for larger aquariums. Refer to video for Joey’s calculations.

Tutorial 2

In this video, the added component is the ceramic stone filtering area, which is similar to how some water filtration units for drinking water are. Otherwise, the mechanics are the same as with the basic sponge filter; water still has to through the sponge first, by virtue of the vacuum created by air bubbles rising from the airstone.

In construction, the massive difference is that the PVC pipe’s function has been replaced by the double-wall tumbler. This is because the tumbler becomes the holding tank for the ceramic filter elements.

Tutorial 3

This video shows a much more simple design, without even using an airstone. The plastic bottle is used to create a housing in which to put the sponge in. One drawback of this design is that you have to fully immerse it and remove all air bubbles for it to sink in the tank correctly. But this is technically a much simpler design, as you do not need to drill holes in anything.

What you need:

• Sponge
• Pipe
• Airline tubing
• 1-liter plastic bottle
• Air pump

This particular design seems to be better used in breeding or fry tanks, where smaller fish can still be affected by the weak vacuum that a sponge filter has.

Tutorial 4

This particular DIY build is unique in that it uses two unique components: the hair curlers, which are “pre-drilled” pipes, and the check valve, which can stop backwash from entering the pump, just in case of power outages. However, this design definitely needs an anchor weight, if it is to be more effective.

The main advantage of this design is that there is no need to cut or drill anything – this is about as pre-made as it gets.

Tutorial 5

The design in this video is similar to Joey Mullen’s, except that no airstone is used, and the bottom end cap attached to the anchor tile has a collar, which makes the sponge rest separate from the tile, exposing more of the sponge’s surface area for filtration.

What you need:

• Sponge; cut to size (check out the video for dimensions), with 10 to 30 pores per inch (PPI)
• PVC Pipe
• Air pump
• Airline tubing – cut to use (see video)
• End cap – must be matched to the pipe, with a stick-out collar
• 90-degree elbow – for use with pipe
• Silicone glue/sealant
• Ceramic or heavy glass tile

The pipe used in this design looks like it’s larger than ¾” in diameter, which could affect the vacuum force for the filter design. However, the larger filtration area because of the end cap collar could be an advantage.

What’s Your Experience?

Have you had a go in making your own sponge filter for your aquarium?

Share your experiences and tips with other fellow hobbyists such as yourselves in the comments section below.

4 thoughts on “[DIY] Make Your Own Aquarium Sponge Filter”

I use an “column” piece of 2 inch wide pvc tube about 10 inches long for a thirty gallon aquarium filter find a clear “cap” to see the vacuum tube working drill hole to the size of the air tubing to run in thru the center of the unit . Cut three triangles @ the opposite end that the cap has been siliconed too. These triangle holes need to be under half an inch wide to create the suction optimum from the air being let into the lowest half of the tube through the air tubing that comes in thru the center the cap and tube through. Also the top cap needs three or four eighth of an inch holes drilled in the top to let the air run thought center column. The center can be filled with allsorts of media for beneficial bacteria to grow on inside this vacuum tube where this tube alspfilters out mechanical waste at the bottom with media such as a sponge plug cut to plug the very bottom from sucking up fry or slow swimmers. I was amazed at how much biological filtration keeps my tank that much more airaided and in the proper h2o zones for healthier aquarium water I’m so amazed at what a little side project turned vital to my balance of my three different tanks

After understanding the principle, I designed mine with two only parts (not counting the airstone and airpump). It is attractive and I think it is possibly the simpliest to build filter in the whole world.

I took a spare water filter cartridge for my home water filter; basically a cylindrical block of filter material with a hole through the middle.

This serves as both the filter media and the inner air passage; no sponge needed, no PVC tubing, no silicon, no plastic bottle, no drilling, etc.

The other piece was something I found to weigh it down and form a base for sitting on the floor of the tank. Many things could be used but I had a 4″ x 2″ drain reducer. The water filter just fit into the 2″ hole.
My airstone was quite large, a one inch sphere, but the reducer base was big enough to accommodate it.

I passed the air line in through the top of the cartridge and attached it to the airstone in the base.